Projectile



I Jam-28, 1947. v FOSTER 2,414,863 v PROJECTILE Filed April 23, 1943 1/ 2 l f J 7 INVENTOR (14/21 M Esme about its own axis.

Patented Jan. 28, 1947 UNITED STATES PATENT OFFICE PROJECTILE Karl M. Foster, "Great Barrington, Mass, assign- 'or of one-half to Frederick A. Pearson, Great J Barrington, Mass.

Application April 23, 1943,Serial'No. l84,235

use'in a smooth bore firearm and formed with rifiing' surface grooves,which produce a pattern of helical ribs, which by their frictional engagement with the barrel of thefirearm and the cartridge shell from which the projectile is discharged, give the projectile a rotary movement The invention relates particularly to a projectile adapted for use in an ordinary shotgun employed for deer hunting and analogous purposes and having either a cylindi-ical or a choked bore.

'The general object of the present invention is to provide an improved projectile of the above mentioned type, and specific objects are to provide a projectile of said type having improved "ballistic propertiesand having a, relatively small heavy metal which forms the body portion of the projectile. The core material may be wood, plastic material or"met'al of relatively low specific gravity, andin' the form of my invention now considered preferable, the core is in the form of fa'body of aluminum or aluminum alloy. having its 'rearendembedded ,in and rig'idly connected toa lead "mass constituting "the body portion of the projectile; and 'having'a specific gravity more than three times that of the core material.

The various "features of novelty which characterize my invention are "pointed out with particularity in the claim annexed to and, forming apart of this-specification. For a better understandingofthe invention however, its advantages and specific objects attained with it, references "should be had to the accompanying drawing and; descriptive matter in which I have illustratedan'd described a preferred embodiment of the invention.

Of the drawing:

Fig. l'is an elevation partly broken away and in section of a shotgun cartridge includin my improved projectile;

Fig. 2 is a section of the projectile shown in Fig. 1 when in its initial condition; and

Fig. 3 is a section of the projectile in the form into which it is compressed or distorted by the pressure in the gun barrel from which it is discharged.

The projectile shown in the drawing comprises a body part A of lead or some other soft, heavy 2 metal, and-a core part B of a material which is harder and of lower specific gravity than the metal used for part A. Advantageously, in many cases, said material of part B is aluminum, The soft part'is generally cylindrical in outline for the major portion of its length, but has its forward end rounded or tapered so that whil the outside diameter of the rear end of the body portion corresponds to the gauge, or barrel dia 'et'er, of the gun from which the projectile is to be discharged, the front end of the soft projectile part Aisappreciably smaller in diameter than the gun barrel.

The projectile-body part A is formed with a deep recess, or cavity a, in its rear end. The

inner surface end of the recess a is a rounded surface, and the side wall A of the recess has aconical inner surface and increases in thickness with its distance from the rear end of the projectile. The conical angle of the side wall of the-recess a is advantageously about 55, and the" diameter of the open rear end of said recess .a may well be about of the outside diameter of the rear end of the projectile, and the depth of the recess a in the unfired projectile may well be about half the maximum projectile diameter. As will be understood, the proportions just stated are given by way of illustration, and not by way of limitation, and they apply to the projectile only when the latter is in its initial or unfired condition shown in Figs. 1 and 2. Helical grooves C are formed on the outer cylindrical surface portion ofthe projectile body A, which may well have about the pitch and relative width indicated inFig. 1. Adjacent grooves are separated by helical ribs D whichmay be fifty thousandths of an inch, in depth.

The projectile core and nose part B'is circular in cross section'and comprises a rounded or ellipsoidal front end or nose portion B and a 'rearwardly extending shank embedded in the projectile body part A. The core part shank may take various forms and as shown, comprises a cylindrical rear end portion B and a cylindrical intermediate portion B the diameter of the latter being less than that of the portion B and less than that of the rear end of the portion B. The projectile soft body part A comprises an annular portion surrounding the core portions B and B and fitting snugly against their surfaces and the rear end surface of the portion B, and which has its outer surface rounded to form a smooth extension of the rounded nose surface of the core part B which merges at its rear end into the cylindrical outer surface of the body part A. In

the form shown, the parts of the core portions B and B which extend radially beyond the periphery of the part B form transversely extending shoulders which interlock with abutting shoulders of the body part A to oppose relative axial movement of the parts A and B. In practice, the core part B may well be a die cast part of aluminum, and the body part A may be formed of lead cast in place on the core part B, and which may or may not be finished by a forging or swaging action.

In Fig, l, the projectile is shown as mounted in a cartridge comprising the usual aper shell E with its rear end mounted in a metal shell F, or

cartridge base, with the usual circumferential ribs F at its rear end. The forward end of the paper shell E is crimped or infolded, and its infolded end E is received in the tapered space between the cylindrical outer portion of the shell E and the rounded forward end core portion B. A column of wads G is interposed between the rear end of the projectile and the explosive material in the rear end of the cartridge.

A cartridge of the general type and form shown in Fig. l is adapted for use in an ordinary shotgun and the cartridge shell and projectile diameters are proportioned to correspond to the gauge of the shotgun, which ordinarily will be 12, 16 or 20, though the invention is adapted for use in the general form illustrated in guns having bores larger than that of a 12 gauge shotgun and smaller than that of a 20 gauge shotgun.

When a gun containing a cartridge of the character shown in Fig, 1 is fired, a pressure of several thousand pounds per square inch is created back of the projectile before the projectile moves clear of the cartridge case of shell, and ordinarily the pressure acting against the rear end of the projectile thereafter increases during the small fraction of a second required to expel the projectile from the gun barrel. The heavy pressure thus acting against the projectile slight- 1y enlarges the outside diameter of the projectile soft body part A the small amount required to make its outer surface bear firmly against the cartridge shell and gun barrel. Furthermore, the pressure compresses or upsets the skirt portion A of the part A which forms the wall surrounding the cavity a. In consequence of the diameter expanding and skirt shortening action of the pressure, the projectile has the form shown in Fig. 3 when it leaves the gun barrel. Advantageously, the parts A and B are so relatively proportioned that the center of gravity of the projectile, when in the form shown in Fig. 3, is approximately midway between the front end of the projectile nose and the plane of the projectile rear end.

With the projectile in the form shown in Fig. 3, and having its center of gravity located as described, the projectile has excellent ballistic properties and practically no tendency to turn end for end or to deviate appreciably from its ideal trajectory. The pressure of the wads acting on the rear end of the projectile s enlarges the projectile as to insure a contact pressure and friction between the projectile ribs D and the surrounding cartridge and gun barrel surfaces which will give the projectile its desired rotary movement. The frictional engagement of the ribs and the cartridge and gun barrel and the force with which the pressure tends to increase the projectile diameter are such as to practically obliterate the grooves C between the ribs D. Test observations indicate that a significant portion of the rotative movement imparted to the projectile is given the latter while it is still in contact with the paper cartridge shell E.

A projectile formed as described and of suitable length and shape to have the desired ballistic properties, may well have a weight which is not more than eighty percent of the weight of a projectile of similar size and outline and formed of lead in the usual manner. Such a reduction in its weight results in a substantial increase in the initial velocity of the projectile and a corresponding flattening of its trajectory, and is thus conducive to accurate shooting and to a desirably high target impacting force. The inclusion in the projectile of a hardened core and nose part insures a desirable projectile penetrating capacity, and a lesser tendency to shatter on impact than would be the case if the projectile were formed wholly of lead, or comprised a core of weak material.

While in accordanc with the provisions of the statutes, I have illustrated and described the best form of embodiment of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claim, and that in some cases certain features of my invention may be used to advantage without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

A projectile for a smooth bore firearm comprising a body part formed of relatively soft, heavy metal and a core part formed of material harder than said metal and having a specific gravity less than one-third that of said metal, said core part being shaped to form the nose portion of the projectile and to form a rearwardly extending shank embedded in and rigidly connected to said body part, the latter being formed with rifling ribs and grooves at its periphery and with a cavity extending into said body part from its rear end with the front end of said cavity in proximity to the rear end of said shank, and with a skirt portion of tapering thickness surrounding said cavity and increasing in thickness from its rear end to its front end, and adapted to be upset by the expelling force acting on the projectile when the latter is being discharged from a firearm, said projectile having its center of gravity approximately midway between its ends after said skirt portion has been upset.

KARL M. FOSTER. 

